package DemoText;
/**
 * 刷题统计
 */

import java.util.Scanner;

public class LuoGuP8708 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long a = in.nextInt(), b = in.nextInt(), n = in.nextInt();
        long week = a * 5 + b * 2;
        long day = n / week * 7;
        n %= week;
        if (n > a * 5) {
            day += 5;
            n -= a * 5;
            day += n / b;
            if (n % b != 0) day++;
        } else {
            day += n / a;
            if (n % a != 0) day++;
        }
        System.out.println(day);
        in.close();
    }

    public static void main1(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = in.nextInt(), b = in.nextInt(), n = in.nextInt();
        int tmp = 0;
        int ret1 = 5, ret2 = 0;
        while (n > 0) {
            if (ret1 != 0) {
                n -= a;
                ret1--;
                tmp++;
            }
            if (ret1 == 0 && ret2 == 0) ret2 = 2;
            if (ret2 != 0) {
                n -= b;
                ret2--;
                tmp++;
            }
            if (ret1 == 0 && ret2 == 0) ret1 = 5;
        }
        System.out.println(tmp);
        in.close();
    }
}
